In a recent draft report, the EPA acknowledged that some scientific studies have found an association between exposure to magnetic fields and increased risk of some kinds of cancer, notably leukemia.

The findings are "controversial and uncertain," the agency says, and each study that detected a risk can be balanced by one that didn't. The EPA won't have any official policy on magnetic fields and cancer until studies are reviewed by a scientific advisory board this month.

So what about those electric blankets?

John Vena, an epidemiologist at the State University of New York at Buffalo, is one scientist who found an increased cancer risk. In a study that compared 382 women with breast cancer and 439 women without the disease, Vena found a possible 30 percent increased risk of breast cancer.

It's not a definitive study, Vena says. The elevated risk is small, and statistically, there's a possibility that the risk doesn't exist.

But, he said, "given the uncertainties out there, it probably would be prudent to use the blanket to heat the bed before you get in it, not through the night."

Scientist Larry Dlugosz of Yale University looked at the possibility that use of electric blankets during pregnancy could increase the risk of birth defects. In a statewide study of New York users, he found no such risk.

But he and Vena note that there are low-magnetic field blankets on the market. Northern Electric, which has about half the market, started making only low-field models more than a year ago.

It's easy enough, says Lee Roszyk, who oversaw the redesign. The blankets have been rewired so that the magnetic field of one wire cancels that of another. Overall, the new blankets have less than 5 percent of the magnetic fields of old blankets. The field given off by the blanket is less than a third of a milligauss, Roszyk said; the Earth's magnetic field is about 500 milligauss.

The low-field blankets are sold under the Sunbeam and Slumberrest brand names. The package has a white dove on it and a brief statement saying it has a reduced magnetic field.